[alsa-devel] HDAudio period/buffer sizes

Raymond Yau superquad.vortex2 at gmail.com
Sun Aug 14 03:44:26 CEST 2011

2011/7/27 Takashi Iwai <tiwai at suse.de>:
> At Tue, 26 Jul 2011 14:23:40 -0500,
> Pierre-Louis Bossart wrote:
>> that the buffer itself was already aligned to 128 bytes from the
>> > very beginning as it's allocated via dma_alloc_coherent().
>> > The fact that the commit fixes the real problem means that the buffer
>> > size must be aligned, too, at least for some hardware.
>> I checked internally and the reply was "There is no requirement the buffer
>> must be 128 byte multiples.  As long as it is integer number of samples, we
>> are good."
>> What's the best way to deal with it? Add a driver option? A compilation
>> option?
> I'd say a driver option since this must be dynamically adjustable.
> Care to make a patch?
> For 3.2 (after 3.1 merge window), we can disable 128-bytes limit as
> default again for testing.  If someone hits the problem, he can switch
> easily and we can investigate more at this time.
The patch seem fix the problem of
snd_pcm_hw_params_set_period_time_near() to 120ms at 11025Hz for those
ad198x codec which are the only HDA codecs which support 11025Hz and

Does it mean that the period_bytes_min =128 can also be removed to
achieve lowest latency ?

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